Field of the Disclosure
The present disclosure relates to semiconductor technology, and more particularly, to dielectrically isolated semiconductor devices and a method for manufacturing the same.
Description of the Related Art
Silicon on insulator (SOI) includes a semiconductor layer and an insulation layer below the semiconductor layer. The insulation layer can be buried oxide layer in a single-crystal silicon substrate. Various semiconductor devices may be formed in SOI, including transistors and diodes, in which the semiconductor layer of the SOI forms active regions of semiconductor devices. Further, the insulation layer isolates the active region of the semiconductor layer from the semiconductor substrate so as to suppress a leakage current through the semiconductor substrate and parasitic capacitance. Thus, the semiconductor devices have some advantages such as high speed, low power consumption and high reliability, if being formed from SOI. For example, transient response speed of a diode is an important parameter when for the purpose of ESD (Electro-Static Discharge) protection. The diode on basis of SOI can operate in high-speed applications due to its decreased parasitic capacitance.
Dielectrically isolated semiconductor devices have active regions which are separated from adjacent semiconductor devices by an insulation layer, and thus have improved device performance. Conventional dielectrically isolated semiconductor devices are formed in SOI, including an insulation layer below an active region, an trench isolation surrounding the active region, and interlayer dielectric layer above the active region. For example, an oxide isolation semiconductor device has an active region almost completely surrounded by an insulation layer, only with conductive vias in the interlayer dielectric layer to reach a doped region. The conductive vias provide electrical connection path from the semiconductor device to external circuits.
Because it is difficult to form single-crystal silicon directly on an oxide layer by epitaxial growth, the dielectrically isolated semiconductor device is typically formed by a process in which an SOI wafer is formed in advance, or formed from a commercially available SOI wafer. Then, an active region of a semiconductor device is formed in a semiconductor layer of the SOI wafer. One of conventional processes for manufacturing the SOI wafer includes bonding an oxide layer and single-crystal silicon in high temperature to have a stack of the single-crystal silicon and the oxide layer as the SOI wafer. This SOI process is complex and expensive, which increases the manufacture cost of the dielectrically isolated semiconductor devices.
Thus, it is desirable to provide a simple process for manufacturing dielectrically isolated semiconductor devices, so that the manufacturing cost is reduced.